This invention relates to orthodontic appliances and their use in the practice of orthodontics. In particular, this invention relates to coiled wire springs and spring clip retention devices which may be prefabricated and readily installed in the mouth to correct malocclusions of teeth and/or jaws.
Most orthodontists correct maloccluded teeth using a system of arch wires that connect all of the teeth. In approximately 60% of orthodontic cases, protrusive anterior teeth are retracted into non-protrusive position. Retraction is normally effected by a tensile force exerted on the arch wires. These tensile forces have heretofore been created by bending springs into the arch wire itself or by using either elastic rubber bands or metallic coil springs.
Springs built into the arch wire itself are extremely difficult for the orthodontist to fabricate and require considerable non-productive time on the part of the orthodontist. Moreover, they are not readily adapted for use between the upper and lower arches of the teeth and create undesired rotations.
Elastic bands have several advantages insofar as they can be inserted and removed by the patient, do not have to be cleaned since they are disposable and do not have to be reactivated by the orthodontist. However, elastic bands have a number of disadvantages. Elastic bands are easily removed by the patient thereby frustrating the orthodontist's efforts and, furthermore, are subject to interaction with the natural fluids in the patient's mouth. This interaction with fluids in the patient's mouth rapidly reduces the physical properties of the conventional strand elastics resulting in a tensile force reduction of about 40% after the elastics have been in place for several hours. Accordingly, the restoring force exerted by the elastic when stretched to a specific elongation does not remain constant and is difficult to control.
Coiled wire spring appliances have been used in orthodontics and such appliances are discussed in U.S. Pat. No. 3,618,214 to M. M. Armstrong entitled "Coiled Wire Spring Appliances for Use in Orthodontics". However, the devices described therein must be tied at each end which is often a difficult procedure especially in the back of the mouth.
It is an object of this invention to provide a coiled spring device which may be readily inserted in the mouth, easily stretched and readily attached to a spring clip retention device without complicated tying procedures.
It is a further object of this invention to provide a coil spring device which may be readily positioned in the mouth and stretched to a predetermined easily discernable degree of elongation thereby applying a predetermined, readily discernable calibrated tensile force to the arch wires and maloccluded teeth.
It is yet another object of this invention to provide a spring clip retention means to which said coil spring device may be readily attached without complicated tying procedure.
These and other objects of this invention may be achieved by an orthodontic treatment assembly for applying repositioning forces to teeth in a patient's mouth comprising, in combination, means suitable for insertion in the mouth to produce a tension force, said force producing means having a plurality of spaced apart positioning means on at least one end, a spring retention device adapted to engage one of said positioning means and further adapted to be mounted on a stable support.
In a preferred embodiment, the means which produces a tension force comprises a resilient element capable of producing a stable and predictable force upon elongation preferably a metallic coil spring. The coil spring itself preferably has a first end, a central coil section, and a second end. Both of the aforesaid ends are capable of being retained when force is applied thereto and at least one end is a substantially straight wire having a plurality of positioning means spaced at predetermined distances from the central coil. The positioning means may be protrusions on the wire such as nodules, crimps, or peenings. A second retention means adapted to retain said second end may also be provided, the resilient element may be elongated to engage said first and second retention means with at least one of the aforesaid positioning means. The amount of force applied to the resilient element will be proportional to the distance of the engaged positioning means from the central coil section.
Ready retention of an end of the spring which end is a substantially straight wire having protruding means therein can be achieved by a spring retention device comprising means for attachment to a fixed support in the mouth and retention means for retaining an orthodontic spring appliance which retention means comprises an element having means therein constructed and arranged to permit a substantially straight wire shaped end of an orthodontic spring appliance to be readily inserted therein and retained when the spring appliance is under tension. Preferably the spring retention device comprises a tube, capable of being threaded onto an orthodontic arch wire, said tube having attached thereto means for retention of an orthodontic spring appliance which means comprises an element attached to said tube, said element having a slot therein constructed and arranged to permit a substantially straight wire shaped and of the aforesaid metallic coil spring to be inserted therein, said element being further constructed and arranged to retain said wire shaped end therein when said spring appliance is under tension.
A readily applied, easily discernable, calibrated tensile force may be achieved by an orthodontic spring appliance comprising means for producing a force, said means having a plurality of spaced apart positioning means on at least one end. Preferably the orthodontic spring appliance comprises a resilient element which produces a stable and predictable force upon elongation, desirably a metallic coil spring suitable for use in a patient's mouth having a first end, a central coil section and a second end, at least one of said ends being a substantially straight wire having protrusions thereon spaced at predetermined intervals from said central coil section, both of said ends constructed to be retained whereby said spring may be stretched to exert a tensile force.
In this invention, the working forces for the orthodontic device are preferably provided by coil wire springs. When the springs are installed in the mouth, the resulting forces on the maloccluded teeth are determined by the characteristics of the unelongated or static springs, and by the extent of spring elongation.
Selection of wire type and diameter and of coil configuration is important in the manufacture of all embodiments. Spring tempered stainless steel wire stock is currently available having satisfactory strength and elastic properties. Knowing the basic physical properties of a particular wire, the determination of spring parameters such as wire diameter, number of coils and coil diameter is readily made by referring to any of the readily available texts on spring design.
To be functional and comfortable, the coil springs of this invention should have a sufficiently small outside diameter so that they can be accommodated in the limited space available in the vestibules of the mouth. Moreover, the springs should also be available in various length to permit use in a variety of positions and to accommodate the wide ranges of intermaxillary spans in the mouths of different patients. Appliance length is readily determinable because other parameters such as wire diameter, cross-section and material, coil diameter and the number of springs can be varied to provide a spring having the desired unelongated or static length and a desired working elongation.